微奈米竹炭混合水溶液之冷凍真空乾燥製程研究

System Process of the Vacuum Freeze Drying for Micro/Nano Bamboo Charcoal Aqueous Solution

李子毅(Tz-Yi Li)

指導教授 ： 鄭鴻斌

國立臺北科技大學/機電學院/能源與冷凍空調工程系碩士班/碩士(2007年)

摘要

製備微奈米材料常存在乾燥的問題，由於將微奈米材料進行充分的乾燥，再行添入各種基材中，可全面提升原有材料之性能，故此處所進行的乾燥技術極為重要。若以維持產品品質與乾燥程度而言，冷凍真空乾燥可使乾燥後的產品有極高的潔淨度與乾燥度。由於其製備過程處與真空狀態，環境中的氣體分子少、密度低，故可使製品保持原有結構，且具高復液性，摻雜入主原料後可充分地進行混合，使產品效能得以提升。本論文針對20%竹炭漿料進行冷凍真空乾燥製程研究，首先以玻璃杯裝盛竹炭漿料進行漿料之共晶點測試與初級乾燥時間的試驗並使用CCD觀測過程樣品的冰線變化，以測得共晶點溫度進而設定初級乾燥棚板溫度，隨後增長初級乾燥時間並固定二級乾燥條件後，以運轉成本與乾燥效率為考量將初級乾燥設定為30分鐘。二級乾燥試驗則是利用不鏽鋼杯與銅杯探討不同材質在不同棚板溫度下對於乾燥速率的影響並找出適當二級乾燥加熱溫度與時間。試驗結果發現此類混合水溶液水份去除的關鍵在於二級乾燥的升溫加熱，實驗曲線二級乾燥過程中樣品出現第二次升溫表示已有近70%的水份遭去除。就容器材質與二級乾燥加熱溫度與時間而言，建議使用鋼杯在二級乾燥予以60℃加熱可有較佳的乾燥速率以及較少的竹炭帶離，而製程中已乾燥竹炭粉末勢必被帶離，可降低溶液深度及減少已乾燥之竹炭遭下層欲昇華水分子帶離之機率。

關鍵字

冷凍真空乾燥 ； 竹炭 ； 凍乾

並列摘要

Drying problem often occurred in preparing micro/nano material, since adding fully dried micro/nano material to various substrates could improve performance of original material completely, hence drying technology here became critically important. In terms of maintaining product quality and drying extent, vacuum freeze drying could ensure dried product with very high cleanliness and dryness. As its preparation process was in vacuum state, gas molecules in ambience were few and of low density, thus product could retain original structure, and have high liquid recovery property, when doped in main material, they could be fully mixed so as to improve product performance. This thesis studied vacuum freeze drying process of 20% bamboo charcoal slurry, first contain bamboo charcoal slurry in glass beaker to run eutectic point test and initial drying time test and observe ice line change of sample with CCD, determine eutectic point and thus set initial drying shelf temperature, then increase initial drying time and fix secondary drying condition, set initial drying at 30min from perspective of running cost and drying efficiency. Secondary drying test used stainless steel cup and copper cup to investigate effect of various material on drying rate at varied shelf temperature and find appropriate heating temperature and time for secondary drying. Test result found that key point of removing water from such kind of mixed aqueous solution lied in heat ramping of secondary drying, in test curve, there emerged the secondary temperature ramping during secondary drying, indicating that near 70% moisture was removed. In terms of container material and secondary drying heating temperature and time, it was recommended to use steel cup and heat at 60℃ during secondary drying, resulted in better drying rate and fewer bamboo charcoal removal, and bamboo charcoal powder already dried in process would be inevitably carried away, so as to reduce solution depth and minimize probability of dried bamboo charcoal being carried away by underlying water molecules to sublime.

並列關鍵字

vacuum freeze drying ； bamboo charcoal ； freeze drying

參考文獻

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